This invention relates broadly to the art of sheet feeders for sequentially feeding forward-most sheets from sheet piles and more particularly to separation enhancers for enhancing separation of forward-most sheets from such piles when they are being fed therefrom.
Sheet feeders for feeding forward-most sheets from sheet piles have long been utilized in graphic art industries as well as in other industries. A pneumatic separation enhancer for such sheet feeders has also been used in which a blow tube having blow holes therein extends across a leading side of a pile for directing streams of air from the blow holes at leading edges of top-most sheets in the sheet pile for creating cushions of air between the sheets and helping to separate a leading edge of a forward-most sheet from the rest of the pile so that it can be more easily gripped or can otherwise avoid false feeds from the pile. In one case, such a tubular blow member has been rotatable so that directions of streams of air coming from the blow holes can be changed and in one case the tubular blow member has had clips thereon at each blow hole which can be rotated about the tubular blow member to partially obstruct the blow holes and thereby also change the direction of fluid streams flowing therefrom. By properly adjusting such a tubular blow member, and its clips, an operator can direct fluid from the blow holes toward a forward edge of a forward-most sheet, particularly at its forward corners, helping to lift the sheet from the pile as well as at leading edges of other sheets immediately below the forward-most sheet for creating thin cushions of air therebetween and thereby helping to separate these sheets from one another. Although this single tubular blow member has proven to be quite beneficial, helping to prevent false feeds, it has several disadvantages. A prime disadvantage of this system is that these many different adjustments take a relatively long time to make. Similarly, such adjustments are necessarily made by trial and error, which makes them inexact, time-consuming and difficult. Along the same line, the clips are difficult to reach when the tubular blow member is mounted on a sheet separation pile feeder, with movable parts being in the same vicinity. Thus, great care and difficulty is required to make the necessary adjustments. Yet another difficulty with the above-described arrangement of a tubular blow member sheet separator is that an undue number of false feeds are obtained therewith. In this regard, such a tubular blow member extending across a leading side of a sheet pile from which forward-most sheets are fed is often not sufficient for both properly lifting corners of the sheets and creating sufficient cushions of air between sheets below the forward-most sheet. Thus, in many cases, such tubular blow members are combined with other tubular blow members positioned along the sides of sheet piles blowing on side edges of sheets in the pile.
For all of these reasons, it is an object of this invention to provide a tubular blow member sheet separation enhancer for a sheet separation pile feeder extending across a front, or leading, side of a sheet pile from which sheets are fed which efficiently enhances the feeding of forward-most sheets from the pile, is relatively easy and convenient to adjust, is not unduly complicated in structure, and can be relatively easily manufactured and installed for use under various conditions.